The use of a release agent to facilitate the unmoulding of hydraulic bonding material, such as concrete is well known. The function of such a concrete mould release agent is to avoid that cured or set concrete adheres to the mould. This can be achieved chemically by retarding the curing process in a very thin outer layer of the concrete body. The chemical action is based on the principle that by delaying or even preventing the curing or setting of a very thin layer of the concrete surface, adherence of the concrete body to the mould is prevented. A release agent should, however, not be too reactive (i.e. not have a too strong curing preventing activity), since this would detrimentally affect the strength of the concrete body. Adherence to the mould of a hydraulic bonding material, such as a cured concrete body can also be avoided physically by applying a hydrophobic release agent to the moulding surfaces so that the cured or set concrete will not adhere to the mould.
Optimal concrete mould release agents show a critical balance between chemical and physical action, depending on the type of concrete.
Effective release agents must, however, not only have an optimal balance between chemical and physical action and adhere sufficiently to the mould, but also exhibit suitable viscosity characteristics and have a minimum hazardous effect on the environment.
Release compositions facilitating the unmoulding of hydraulic bonding material, such as concrete, are normally based on mineral oil to which kerosene has been added to adjust the viscosity and comprise additives such as retarding agents for improving the release properties, wetting agents, corrosion inhibitors, etc. The use of a mineral oil involves, however, a considerable health risk since a mineral oil may cause skin irritancy and eczema and, when used in sprayed form, lung diseases. The use of mineral oils also entails an environmental disadvantage, since mineral oils are poorly biodegradable.
There is therefore still a need for biodegradable release compositions for facilitating the unmoulding of hydraulic bonding material, such as concrete but also mud bricks, which are effective, harmless and have a minimal impact on the environment.
It is an object of the present invention to provide effective, non-toxic, non-irritant and biodegradable concrete mould release agents. It has now been found that the object of the present invention can be achieved by mineral oil and kerosene free concrete mould release compositions, based on oil and water emulsions of certain fatty acid esters, preferably oil-in-water emulsions.